Adds SITL demo.
Adds SITL demo.

dronekit/dronekit-python,diydrones/dronekit-python,duststorm/dronekit-python,hamishwillee/dronekit-python,hamishwillee/dronekit-python,trishhyles/dronekit-python,diydrones/dronekit-python,trishhyles/dronekit-python,duststorm/dronekit-python,dronekit/dronekit-python